1. Field of the Invention
The present invention relates to a cage for experimental animals, such as mice, rats or hamsters, employing optical sensors to measure the action of the experimental animal.
2. Description of the Prior Art
In the medical and pharmaceutical fields, main affection of activity of medicines and an approximate result of a sudden poison are evaluated on the basis of observation of a wide range of symptoms or behavioral movement associated with experimental animals as a result of dosage of chemical and analogous chemicals which becomes the raw material of the medicines. Furthermore, a long term experiment is obligatory for the medicines and foods in view of safety thereof.
The behavioral movements of the experimental animals are deeply related with a neural system of the animals. The behavioral movement of the animals always includes movement in the form of walk. Observing the change of position of the behavioral movement of the experimental animal revealed one aspect of the experimental animals and infers the part of the function of the neural system from dosage of new medicine supplies. However, inasmuch as the experimental animals are very small such as the mice, and the rats, it is very difficult to observe the positional change of the behavioral movement of the experimental animals. Hence, it is difficult to observe visually the full particulars of the positional change of the experimental animals. The positional change means the behavioral movement of the experiment animals kept in a keeping cage such as rightward and leftward movements to turn the body thereof in the keeping cage. The keeping cage employed for measurement of positional change of the experiment animals is conventionally typically square shaped.
A prior art keeping cage is illustrated in FIG. 1. A square-shaped cage body 1 made of polycarbonate, stainless, or aluminum and a cover of metal net made of stainless wire. A mouse M as an experimental animal is kept in the cage body 1. Light-emitting diode LEDs 3 and light receiving transistors 4 functioning as a detector are respectively oppositely disposed in X-axis and Y-axis for detecting the positional change of the mouse M in the X-axis and Y-axis directions. The detector composed of the LEDs and the light receiving transistors 4 detects the X-axis direction and Y-axis direction to thereby issue an electric signal which is amplified by an amplifier (not shown) so that the positional change is automatically measured by numeration and analyzation per unit time.
However there is such a problem in prior art square shaped keeping cage that progress direction of the experiment animal is hindered by a side wall unless the keeping space is not so large, at the time the experiment animal behaves to change its position in the cage, to thereby restrict a continuous behavioral movement of experimental animal. As a result, the experiment animal repeats turning of directions physically without voluntary behavial movement, which is not affected by the behavioral movement thereof affected by the neural system caused by the dosage of the medicine. That is, the obstacle of the progress direction of the experimental animal causes a behavioral data to introduce an incorrect factor which results in achieving unideal cage.